1. Field of the Invention
This invention relates to a calculation of camera position (photographing position) in a photogrammetric analytical measurement system, in which a survey map is produced on the basis of a set of photographed pictures obtained at two different photographing positions.
2. Description of the Related Art
For example, photogrammetry is carried out at a traffic accident spot. The traffic accident spot is photographed by a camera in at least two different positions, and a survey map of the traffic accident spot is produced based on a set of photographed pictures obtained at the different positions.
In particular, a two-dimensional coordinate system is defined on each of the photographed pictures, and two-dimensional positions of the objects, which are recorded on each picture, are determined by the two-dimensional coordinate system. Then, a three-dimensional coordinate system is defined on the basis of the two sets of two-dimensional coordinate systems, and three-dimensional positions of the recorded objects are determined from the three-dimensional coordinate system. Accordingly, it is possible to produce a survey map of the traffic accident spot by drawing the objects on a sheet of paper in such a manner that the objects are projected on one of the three planes defined by the three-dimensional system.
Before accurately scaled distances and lengths can be reproduced on the survey map, a standard measurement scale must be recorded together with the objects in the photographed pictures. Also, a standard reference plane, on which the survey map should be drawn, must be defined in the photographed pictures.
Usually, in order to define the standard measurement scale and the reference plane, three respective cone-shaped markers, which are identical to each other, are positioned at suitable locations around a traffic accident spot. Namely, a distance between two apexes of the cone-shaped markers is measured, for example, with a measuring tape, and set as the standard measurement scale, and a plane, defined by the three apexes of the cone-shaped markers, is utilized as the reference plane. As the positioning of the cone-shaped markers and the measurement of the distance between the two apexes are performed by operators, a process of preparing for photographing is onerous and requires a lot of time.
In order to solve the above mentioned problems, photogrammetric analytic measurement, using a target which has a triangular frame instead of the three cone-shaped markers, is disclosed in Japanese Unexamined Patent Publication (Kokai) No. P10-221072. Standard point members are respectively mounted on each of three apexes of the target. A distance between the standard point members is set as the standard measurement scale, and a plane defined by the standard point members is utilized as the reference plane. A reflecting sheet, for example, is attached on the standard point members so that the standard point members can be viewed easily in photographed pictures.
The determination of the three-dimensional positions of the recorded objects from the three-dimensional coordinate system is carried out by iterating a series of approximate calculations, using a computer having a monitor on which the set of photographed pictures is displayed.
Initially, before a first series of approximate calculations is executed, the standard point members and a suitable point on one of the recorded objects in the set of photographed pictures displayed on the monitor, are selected with a cursor, by manipulating a mouse, whereby three sets of two-dimensional coordinates, corresponding to the standard point members, and a set of two-dimensional coordinates on the suitable point of the selected object are inputted to the computer. Namely, the execution of the first series of approximate calculations is based upon the inputted two-dimensional coordinates of the standard point members and the inputted two-dimensional coordinates of the suitable point on the selected object, thereby determining three-dimensional positions of the standard point members and a three-dimensional position of the suitable point of the selected object from the three-dimensional coordinate system.
Then, another suitable point on the selected object in the set of photographed pictures displayed on the monitor is indicated with the cursor, by manipulating the mouse, whereby a set of two-dimensional coordinates of the other suitable point on the selected object is inputted to the computer, and a second series of approximate calculations is executed on the basis of the inputted two-dimensional coordinates of the other suitable point on the selected object, thereby determining a three-dimensional position of the other suitable point on the selected object from the three-dimensional coordinate system. This procedure is continued until a sufficient number of points on the selected object are indicated, to thereby specify a three-dimensional profile of the selected object.
The aforementioned series of approximate calculations is executed based on positional data of the camera at which the pictures are photographed. The positional data of the camera includes a distance from the camera to the selected object, an angle of the camera against the object. The positional data of the camera is calculated based on the two-dimensional coordinates of the standard point members selected by the operator.
However, it takes a comparatively long time to select the standard point members in the set of photographed pictures displayed on the monitor, with the cursor, by manipulating the mouse. Therefore, when there are a lot of the photographed pictures, it becomes onerous for the operator to operate the above mentioned manipulation of the mouse. Further, the accuracy of the photogrammetric analytic measurement is dependent upon the skill of the operator.
Therefore, an object of the present invention is to provide a device for calculating positional data of standard points of a target of photogrammetric analytic measurement.
In accordance with an aspect of the present invention, there is provided a device, for calculating positional data of standard points of a target of photogrammetric analytic measurement, comprising an image data obtaining processor and a value of two-dimensional coordinates calculating processor.
The image data obtaining processor photographs an object of photogrammetric analytic measurement with a target that has a first standard point and a second standard point and a third standard point.
Each length of distance between the first standard point and the second standard point and the third standard point is predetermined. An angle defined by a first straight line connecting the first standard point and the second standard point, and a second straight line connecting the second standard point and the third standard point, is predetermined. A number of assistant points provided on the first straight line and a number of assistant points provided on the second straight line are different.
The value of two-dimensional coordinates calculating processor calculates each two-dimensional coordinate value of the first standard point, the second standard point and the third standard point in a photograph coordinate system that is a two-dimensional coordinate system of a photographed image, obtained by the image data obtaining processor, after determining each position of the first standard point, the second standard point and the third standard point in the photographed image, by comparing the number of the assistant points provided on the first straight line and the number of the assistant points provided on the second straight line.
The first standard point, the second standard point, the third standard point and the assistant points provided on the first straight line and provided on the second line are made of a reflecting material, such that the first standard point, the second standard point, the third standard point and the assistant points have a relatively higher brightness than other objects in the photographed image.
The value of two-dimensional coordinates calculating processor is provided with: a binarization processor that classifies each pixel composing of digital image data of the photographed image into a high brightness class and a low brightness class after comparing a brightness of each pixel with a predetermined threshold value; a group extracting processor that extracts groups in which a plurality of the pixels of the high brightness class sequentially exist in the digital image data, an area of which is within a predetermined range; a calculating processor that calculates a value of two-dimensional coordinates of a center of gravity of each of the groups, based on the brightness of each pixel composing the groups and a value of coordinates of the each pixel in the photograph coordinate system; a first points range extracting processor that extracts a first points range on which a plurality of the centers of gravity lie, a number of the plurality of the centers of gravity on the first points range being equal to a total point number including the first standard point, the second standard point and the number of the assistant points on the first straight line; a second points range extracting processor that extracts a second points range on which a plurality of the centers of gravity lie, a number of the plurality of the centers of gravity on the second points range being equal to a total point number including the second standard point, the third standard point and the number of the assistant points on the second straight line; a combination extracting processor that extracts a combination of the first points range and the second points range in which the first points range and the second points range share the center of gravity of an identical end point; and a standard point determining processor that determines a center of gravity of an end point of the first points range selected by the selecting processor, being opposite to the identical end point shared by the first points range and the second points range, as the first standard point, determines the center of gravity of the identical end point shared by the first points range and the second points range as the second standard point, and determines a center of gravity of an end point of the second points range selected by the selecting processor, being opposite to the identical end point shared by the first points range and the second points range, as the third standard point.
The number of the assistant points provided on the first straight line is two, and the number of the assistant points provided on the second straight line is one, so that the first points range is a four points range in which four centers of gravity range on a same straight line in the photographed image, and the second points range is a three points range in which three centers of gravity range on a same straight line in the photographed image.
In accordance with another aspect of the present invention, there is provided a method for calculating positional data of standard points of a target of photogrammetric analytic measurement comprising: a first step that photographs an object of photogrammetric analytic measurement with a target that has a first standard point and a second standard point and a third standard point, by a camera; and a second step that calculates each two-dimensional coordinate value of the first standard point, the second standard point and the third standard point in a photograph coordinate system that is a two-dimensional coordinate system of a photographed image photographed by the camera.
Each length of distance between the first standard point and the second standard point and the third standard point is predetermined. An angle, defined by a first straight line connecting the first standard point and the second standard point, and a second straight line connecting the second standard point and the third standard point, is predetermined. A number of assistant points provided on the first straight line and a number of assistant points provided on the second straight line are different.
In the second step, each two-dimensional coordinate value of the first standard point, the second standard point and the third standard point in the photograph coordinate system, after determining each position of the first standard point, the second standard point and the third standard point in the photographed image based on a difference between the number of the assistant points provided on the first straight line and the number of the assistant points provided on the second straight line.
In accordance with another aspect of the present invention, there is a provided a recording medium in which a calculating program of standard points of a target of photogrammetric analytic measurement is stored.
The target has a first standard point and a second standard point and a third standard point. Each length of distance between the first standard point and the second standard point and the third standard point is predetermined. An angle, defined by a first straight line connecting the first standard point and the second standard point, and a second straight line connecting the second standard point and the third standard point, is predetermined. A number of assistant points provided on the first straight line and a number of assistant points provided on the second straight line are different.
The calculating program comprises: a values of two-dimensional coordinate calculating routine that calculates each two-dimensional coordinate value of the first standard point, the second standard point and the third standard point in a photograph coordinate system that is a two-dimensional coordinate system of a photographed image, photographed in such a manner that an object of photogrammetric analytic measurement is photographed with the target by a camera, after determining each position of the first standard point, the second standard point and the third standard point in the photographed image based on a difference between the number of the assistant points provided on the first straight line and the number of the assistant points provided on the second straight line.